Sometime, it is slow to access Magneto official developer documents, luckily, Magneto provide fully document in its Github,  we can download it and build on our local Ubuntu OS, the details is as follows.

In order to build the documentation, we need ruby 2.0 up, check if you OS already has ruby installed:

if you have ruby installed, but its version is lower then 2.0, you need to remove the old version ruby and then install new ruby:

Now install new ruby version:

Important: the ruby2.0-dev is needed for install bundle.

We can also install a ruby switcher, so we can switch default ruby version:

Then, install bundler:

Now download Magento Developer Documenttation from github.

Extract the downloaded zip file and cd to documentation directory, then run:

And finally:

if you got error message related with Javascript, install node.js:

and then re-run bin/jekyll serve, wait a while, screen prompt: Server running … press ctrl -c to stop. now you can access full Magneto developer documentation at:

http://localhost:4000 now.